Product identification labels are now viewed as a critical mechanism for maintaining compliance, ensuring brand consistency, improving operational efficiency, combating fakes and supporting business growth. Selecting the optimal label type and material is crucial.
Selecting the right label to identify a finished product drives business efficiency and realize greater value by ensuring high-quality print and durability throughout the product’s life. Product identification labels are the final link between a company and its key stakeholders including customers, consumers, care-givers, patients, and regulators.
There are thousands of types of thermal labels, and not all are created equal. Each material features different attributes that enable it to be utilized in different environments. It is critical that the labels utilized are not only readable and scannable when they leave an operation, but throughout the products safe and appropriate use and disposal. This will reduce risk of non-compliance to government and industry mandates. There are specific guides on how to select the optimal material to identify a product by reviewing thermal printing basics, identifying the key considerations needed to be mindful of and what to look for in a supplier.
Thermal printing
Before selecting a label solution, it is important to understand the differences between direct thermal and thermal transfer printing technologies. Each method uses a thermal printhead that applies heat to the surface being marked. Thermal transfer printing uses a ribbon to produce durable, long-lasting images on a wide variety of materials. Direct thermal printing does not use a ribbon and instead creates the image directly on the printed material.
Direct thermal printing uses chemically treated, heat-sensitive media that blackens when it passes under the thermal printhead. Direct thermal printers have no ink, toner, or ribbon. Direct thermal materials offer a shorter life than thermal transfer, and may fade over time. Direct thermal labels offer minimal resistance to heat, light, abrasion, and chemicals. Exposure to these items will cause the material to darken, resulting in the text and bar codes that are unreadable. For these reasons, direct thermal printing is not used for demanding applications.
In thermal transfer printing, a thermal printhead applies heat to a ribbon, which melts ink onto the material to form the image. This technique provides image quality and durability that is unmatched by other on-demand printing technologies.
Thermal transfer offers a wider variety of materials than direct thermal, including paper, polyester, vinyl, polypropylene and polyimide materials. Thermal transfer solutions are much more durable than direct thermal, as they are resistant to a wider variety of temperatures and chemicals. To obtain resistance to very demanding environments, the specific label material and ribbon must be carefully matched.
Transfer ribbons
By selecting the right material-ribbon combination, as well as specialty adhesives, users can create archival-quality labels to withstand temperature extremes, ultraviolet exposure, chemicals, sterilization, and more. Thermal transfer ribbons are available in wax, wax-resin, and resin formulations that meet the durability requirements of a wide range of labeling applications:
- wax ribbons – designed for applications that use paper facestocks in environments with little to no exposure to weak chemicals and/or exposure to moderate abrasion.
- wax/resin ribbons – optimized for use with select paper and matte synthetics in environments with moderate to extreme chemical exposure and/or exposure to moderate abrasion, or where UL/cUL approval is required.
- resin ribbons – designed for use with synthetic materials in environments with harsh to extreme chemical exposure and/or exposure to excessive abrasion, and where UL/cUL approval is required.
Optimal print technology
In order to identify the optimal print technology, material and ribbon (if thermal transfer printing), to ensure that the label remains readable during the products safe and appropriate use and disposal, the following should be considered:
Surface
The type and the shape of surface being labeled needs to be considered to ensure that the label remains adhered to the surface. Sometimes a specific label does not adhere as well to a plastic bin as it does to a cardboard box. This is because these items have a different surface energy. The shape of the surface is also important to consider. For example, small curved surfaces are also difficult to label, since they require a flexible material with a tight mandrel adhesive to make sure the label does not pull away from the surface.
Extreme temperatures
Materials and adhesives are also sensitive to very low and very high temperatures. There are two types of temperatures necessary to consider – application temperature and service temperature.
The application temperature is the temperature in which the label is being applied. For example, a new test tube is taken out of a box at room temperature, and a label is applied, the application temperature is 70ºF (21ºC).
Service temperature is the temperature range in which the label will be used. For example, the same test tube is filled with a sample and cryogenically stored. Sometime later, it is thawed and sterilized with steam. The service temperature range is -112ºF (-80ºC) to 212ºF (100ºC).
Standard materials generally perform well when an application temperature is a minimum of 25 degrees F and in service temperatures ranging from -65 degrees F to 200 degrees F. Labeling in conditions outside of this range requires the use of a thermal transfer solution and normally requires a specialty adhesive to insure that the label remains secured.
Resistance
Contact and rubbing will affect readability over time. If in an application, the label will come into contact with items that could scratch it and make it unreadable, a ribbon with a higher resin content will provide improved resistance. When a label will be exposed to moderate to extreme chemicals, a thermal transfer labeling solution is required. In the case of harsh and extreme chemicals, a high-durability resin ribbon is also recommended. Weak chemicals include window cleaners, water, while moderate chemicals include alcohol and bleach; harsh chemicals are gasoline and oil and extreme chemicals include acetone and xylene.
Lifespan
If a product will be subjected to the elements outdoors (rain, sun, etc.), a thermal transfer synthetic material would be the optimal solution, as the label and the image provide the added durability required to survive these tough environmental factors.
Knowing how long the label will need to be readable for in addition to the environmental factors will help identify the optimal solution. For example, if the label only requires readability for six months and does not need to resist chemicals, moisture, and abrasion, a direct thermal paper label would best meet the needs. However, if the label will be subjected to moderate chemicals and be on an item that will be stored outside for over three years, a specialty thermal transfer synthetic label would be required.
Label format
If the format includes rotated (ladder) bar codes, detailed graphics, or international characters, this will affect the print speed and print darkness.
Print speed is another key consideration, as material and ribbon selection will influence the maximum print speed. Typically, synthetic labels do not produce quality text and barcodes above 6 ips, and in order to print at 12 ips or higher a thermal transfer paper label with a high-speed wax ribbon is required.
Increasing the print darkness is necessary when printing at faster speeds to get the best bar code grades and print quality. When using higher-grade ribbons, which require additional energy, a higher print darkness is also required. Using a printer with a higher DPI is necessary when printing formats with detailed graphics and/or small fonts. However, to properly resolve the format, you will also need to use a material with a very smooth or gloss surface, such as a synthetic.
If an applicator is to be used this must be known up front as the label must be cut differently so that it peels off properly from the liner. In addition, perforations are also not recommended as they change the stiffness characteristics of the label making the label difficult to release from the liner.
Required certifications
When choosing a thermal printer supplier, be sure to work only with a vendor that has the required certifications for your industry, quality controls in place and does not substitute materials run-to run.
For an electronics manufacturer that UL lists its products, choose a supplier listed on UL site that offers label and ribbon solutions that are UL certified. There is a separate UL certification required for suppliers to be able to pre-print the UL mark. Suppliers with ISO certifications have standard, consistent procedures and processes in place to ensure high-quality products are produced.
If an application requires that the supplier uses pre-printed colored text, symbols or logos, ensure that the supplier utilizes an automated color mixing system that includes color-matching software. This enables the supplier to match requested PMS color closely and store that formulation within their system so that the color is consistent from run-to run.
It is also necessary to validate that the supplier has an automated vision inspection system on press to ensure proper placement of pre-printed text throughout the manufacturing process
Print quality problems can occur when label rolls have excessive dust. This dust can accumulate on label rolls during the manufacturing process, and then accumulate on the printhead resulting in text and barcode quality issues, and increased printhead replacement over time. Therefore, the supplier needs to have processes in place to sharpen dies on a regular basis and has a trim removal and vacuum system in place to reduce dust. No two materials are created equal. That is why it is important to understand a supplier’s materials substitution policy. The use of slightly different materials from run-to-run can require the adjustment of the print darkness on the printer to enable high-quality images.
by Zebra Technologies